The present invention relates to a defect testing apparatus and a defect testing method for inspecting a state of generation of defects such as foreign particles in a fabrication process such as a semiconductor fabrication process, a liquid-crystal-display fabrication process and a print-board fabrication process wherein a defect such as a foreign particle generated in a process to create a pattern on a substrate to produce an object is detected and analyzed in order to determine a countermeasure.
In the conventional semiconductor fabrication method, a foreign particle existing on a semiconductor substrate also known as a wafer causes a defect such as poor insulation of a wire or a short circuit. Furthermore, in the case of a miniaturized semiconductor device, an infinitesimal foreign particle existing in a semiconductor substrate results in poor insulation of a capacitor or destruction of typically a gate oxide film. These foreign particles are introduced to get mixed with a semiconductor material in a variety of states due to a variety of causes For example, a foreign particle is generated by a movable part of a transportation apparatus or a human body A foreign particle can also be generated as a result of a chemical reaction in processing equipment using a process gas or mixed with chemicals or a raw material.
Likewise, if a foreign particle is introduced to get mixed with a pattern, causing some defects in a process to fabricate a liquid-crystal display device, the resulting display device is not usable. The process to fabricate a print board is in the same situation, That is to say, a mixed foreign particle causes a poor connection and a short circuit in a pattern.
One of publications for detecting a foreign particle on a semiconductor substrate of this type is disclosed in Japanese Patent Laid-open No. Sho 62-89336 and referred to hereafter as publication 1. According to this prior art, a laser beam is radiated to a semiconductor substrate. If a foreign particle is stuck to the semiconductor substrate, the foreign particle will generate scattered beams which can then be detected and compared with a result of inspection for a semiconductor substrate of the same type inspected immediately before. In this way, a difference in inspection result can be detected and used to eliminate a pattern defect. As a result, a foreign particle and a defect can be detected with a high degree of sensitivity and a high degree of reliability. Another publication referred to hereafter as publication 2 is disclosed in Japanese Patent Laid-open No. Sho 63-135848. According to this publication, a laser beam is radiated to a semiconductor substrate. If a foreign particle is stuck to the semiconductor substrate, the foreign particle will generate scattered beams which can then be detected. A detected beam generated by a foreign particle is analyzed by using an analysis technique such as laser photo luminescence or a secondary X-ray analysis (XMR).
In addition, as a technology for detecting a foreign particle, there is also known a technique whereby a coherent beam is radiated to a wafer, and the beam reflected by repetitive patterns on the wafer is removed by˜ a spatial filter to emphasize light components generated by a foreign particle or a defect which does not exhibit repetitiveness. In this way,' a foreign particle or a defect can be detected.
A technology disclosed in Japanese Patent Laid-open No. Hei 1-117024 is referred to hereafter as publication 3. According to this publication, in a foreign particle inspecting apparatus, a beam is radiated to a circuit pattern on a wafer in a direction forming an angle of 45 degrees with respect to a group of main straight lines of the circuit pattern and a 0th-order diffracted beam from the group of main straight lines is introduced into the aperture of an objective lens. The disclosure also includes a description which states that, according to publication 3, a beam from any group of straight lines other than the group of main straight lines is shielded by a spatial filter.
In addition, other publications related to apparatuses and methods for detecting defects such as foreign particles are disclosed in Japanese Patent Laid-open No. Hei 1-250847, Japanese Patent Laid-open No. Hei 6-258239, Japanese Patent Laid-open No. Hei 6-324003, Japanese Patent Laid-open No. Hei 8-210989 and Japanese Patent Laid-open No. Hei 8-271437 and referred to as publications 4, 5, 6 ,7 and 8 respectively.
With publications 1 to 8 mentioned above, however, it is impossible to detect a defect such as an infinitesimal foreign particle on a substrate, on which repetitive patterns coexist with non-repetitive patterns, at a high speed, with ease and with a high degree of sensitivity.
To put it in detail, publications 1 to 8 have a problem of a substantially reduced sensitivity (increased minimum dimensions of a detected foreign particle) in the case of a part of the substrate other than the repetitive portion such as memory cells.
In addition, publications 1 to 8 also have a problem of a substantially reduced sensitivity in the case of an oxide film which passes a radiation beam.
Moreover, publications 1 to 8 also have a problem of inability to detect a defect such as an infinitesimal foreign particle.
Furthermore, in the case of publications 1 to 8, a mass-production build-up line or a pilot line and a mass-production line of a semiconductor production process are not distinguished from each other. That is to say, inspection equipment used in the mass-production build-up work is also used in a mass-production line without change in spite of the fact that it is necessary to early detect generation of a foreign particle on the mass-production line and determine a countermeasure for the detected foreign particle.
At any rate, the conventional defect inspecting apparatus is large in size and has such a configuration that the apparatus must be installed independently. For this reason, in order to inspect a foreign particle and a defect, it is necessary to transport a semiconductor substrate, a liquid-crystal-display substrate or a print substrate which has been processed along the mass-production line to a place at which the defect inspecting apparatus is installed. That is to say, it takes time to transport the substrate and to inspect the substrate for a foreign particle and a defect. As a result, complete inspection is difficult. In addition, it is hard to carry out such sampling inspection at a sufficiently high frequency.
Further, a defect inspecting apparatus with such a configuration requires an operator.